Geometric figure which approximates the Earth's shape
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Geodesy
Fundamentals
Geodesy
Geodynamics
Geomatics
History
Concepts
Geographical distance
Geoid
Figure of the Earth (radius and circumference)
Geodetic coordinates
Geodetic datum
Geodesic
Horizontal position representation
Latitude / Longitude
Map projection
Reference ellipsoid
Satellite geodesy
Spatial reference system
Spatial relations
Vertical positions
Technologies
Global Nav. Sat. Systems (GNSSs)
Global Pos. System (GPS)
GLONASS (Russia)
BeiDou (BDS) (China)
Galileo (Europe)
NAVIC (India)
Quasi-Zenith Sat. Sys. (QZSS) (Japan)
Discrete Global Grid and Geocoding
Standards (history)
NGVD 29
Sea Level Datum 1929
OSGB36
Ordnance Survey Great Britain 1936
SK-42
Systema Koordinat 1942 goda
ED50
European Datum 1950
SAD69
South American Datum 1969
GRS 80
Geodetic Reference System 1980
ISO 6709
Geographic point coord. 1983
NAD 83
North American Datum 1983
WGS 84
World Geodetic System 1984
NAVD 88
N. American Vertical Datum 1988
ETRS89
European Terrestrial Ref. Sys. 1989
GCJ-02
Chinese obfuscated datum 2002
Geo URI
Internet link to a point 2010
International Terrestrial Reference System
Spatial Reference System Identifier (SRID)
Universal Transverse Mercator (UTM)
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A scale diagram of the oblateness of the 2003 IERS reference ellipsoid.
Ellipse with the same eccentricity as that of Earth, with north at the top
Circle with diameter equal to the ellipse's minor axis
Karman line, 100 km (62 mi) above sea level
Altitude range of the ISS in low Earth orbit
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations.
It is a spheroid (an ellipsoid of revolution) whose minor axis (shorter diameter), which connects the geographical North Pole and South Pole, is approximately aligned with the Earth's axis of rotation. The ellipsoid is defined by the equatorial axis (a) and the polar axis (b); their radial difference is slightly more than 21 km, or 0.335% of a (which is not quite 6,400 km).
Many methods exist for determination of the axes of an Earth ellipsoid, ranging from meridian arcs up to modern satellite geodesy or the analysis and interconnection of continental geodetic networks. Amongst the different set of data used in national surveys are several of special importance: the Bessel ellipsoid of 1841, the international Hayford ellipsoid of 1924, and (for GPS positioning) the WGS84 ellipsoid.
An Earthellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy...
the Earth. A spheroid describing the figure of the Earth or other celestial body is called a reference ellipsoid. The reference ellipsoid for Earth is...
seven climes). The realization that the figure of the Earth is more accurately described as an ellipsoid dates to the 17th century, as described by Isaac Newton...
An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation...
same volume as the ellipsoid (R3). All three values are about 6,371 kilometres (3,959 mi). Other ways to define and measure the Earth's radius involve the...
geodesics on an ellipsoid arose in connection with geodesy specifically with the solution of triangulation networks. The figure of the Earth is well approximated...
triad is also known as Earthellipsoidal coordinates (not to be confused with ellipsoidal-harmonic coordinates or ellipsoidal coordinates). Longitude...
"Universal Transverse Mercator WGS 84 Zone 16N") comprises a choice of Earthellipsoid, horizontal datum, map projection (except in the geographic coordinate...
ellipsoid to that point Q on the surrounding sphere (of radius a) which is the projection parallel to the Earth's axis of a point P on the ellipsoid at...
standards, also includes a choice of geodetic datum (including an Earthellipsoid), as different datums will yield different latitude and longitude values...
The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution...
Earth section paths are plane curves defined by the intersection of an earthellipsoid and a plane (ellipsoid plane sections). Common examples include...
was a way to determine the figure of the Earth, whose crucial parameter was the flattening of the Earthellipsoid. In the 18th century, in addition of its...
precipitation, allowing components such as nitrogen to cycle. Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest...
dimensions of the Earthellipsoid axes were defined by logarithms in keeping with former calculation methods. The Bessel ellipsoid fits especially well...
several parts: a model for Earth's shape and dimensions, such as a reference ellipsoid or a geoid; an origin at which the ellipsoid/geoid is tied to a known...
in cartography and geodesy the Earth is often approximated by an oblate spheroid, known as the reference ellipsoid, instead of a sphere. The current...
deviations of the actual surface from the ellipsoid, including the tallest mountains and deepest oceanic trenches. Earth's rotation also affects the sea level...
determine a figure of the Earth. One or more measurements of meridian arcs can be used to infer the shape of the reference ellipsoid that best approximates...
been replaced as the "International ellipsoid" by the newer Lucerne ellipsoid (1967) and GRS 80 (1980). Earthellipsoid Defense Mapping Agency: Geodesy for...
is a public registry of geodetic datums, spatial reference systems, Earthellipsoids, coordinate transformations and related units of measurement, originated...
(Central Bureau of International Geodesy), and a series of global ellipsoids of the Earth were derived (e.g., Helmert 1906, Hayford 1910/ 1924). A unified...
surface of the Earth. Common abstractions for the surface between two geographic points are: Flat surface; Spherical surface; Ellipsoidal surface. All abstractions...
gravity on Earth's surface by means of a mathematical model representing Earth. The most common model of a smoothed Earth is a rotating Earthellipsoid of revolution...
Moon is a very slightly scalene ellipsoid due to tidal stretching, with its long axis displaced 30° from facing the Earth, due to gravitational anomalies...
determined by methods of astrogeodesy and is chosen as ellipsoidal latitude and longitude at the Earthellipsoid which is used to calculate the coordinates of...
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